I agree with the above posts. And with the advice you've gotten on your other thread - your trip will be better if you drop at least one destination, and spread that time around your other destinations, so you're not moving around so much. I know that, especially for a first trip, the temptation to want to "see it all" is great. But do resist - or you'll be sorry once you're there. The oft-repeated mantras really are true:
1) Two nights in a place equals only one full day
2) You lose at least a half day changing locations, even if they're close together.
Definitely, if you do want to see the Berner Oberland, stay right there, in Lauterbrunnen, Gimmelwald, Wengen, or Mürren. Do not stay in Interlaken, which is near but not in the Lauterbrunnen valley. Of course, if you must have an Asian restaurant, a huge supermarket, or large tour groups as part of your Alps experience, stay in Interlaken.
As posted on the other thread, both Geneva Airport and Zurich Airport have train stations right inside, so you do not need to stay in those cities for your first day, but can take a train upon arrival right from the airport to somewhere else.
To find train travel times and routes, use the Bahn website http://reiseauskunft.bahn.de/bin/query.exe/en, following Rick's tutorial: http://www.ricksteves.com/travel-tips/transportation/trains/online-schedules